Magnetoresistive head with spin valve configuration

ABSTRACT

The present invention relates to a magnetoresistive head capable of converting a change in a magnetic field generated by a magnetic recording medium into a change in electric resistivity by utilizing spin valve magnetoresistance effect to read signal information. The magnetoresistive head comprises a first magnetic layer, a second magnetic layer formed on the first magnetic layer through a first nonmagnetic metal layer and magnetized in one direction, a third magnetic layer formed on the second magnetic layer through a second nonmagnetic metal layer, and an electric current supplying layer for applying a constant current to at least the third magnetic layer, the second nonmagnetic metal layer and the second magnetic layer in one of the same direction as and the opposite direction to the direction of magnetization of the second magnetic layer.

This is a divisional of copending application Ser. No. 08/503,006 filedon Jul. 17, 1995 .

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetoresistive head and, moreparticularly, a magnetoresistive head capable of reading signalinformation by converting a change in magnetic field generated from amagnetic recording medium into a change in electric resistivity by useof spin valve magnetoresistance effect, upon reading information signalfrom the magnetic recording medium.

2. Description of the Prior Art

As a device for reading information signals from the magnetic recordingmedium such as a hard disk, a magnetic card, a magnetic tape, themagnetoresistive head employing the spin valve magnetoresistance effecthas been proposed in Patent Application Publication (KOKAI) U.S. Pat.No. 5,206,590.

The magnetoresistive head has a structure shown in FIGS. 1A and 1B, forexample.

In FIGS. 1A and 1B, a lower ferromagnetic layer 2, a nonmagnetic metallayer 3, an upper ferromagnetic layer 4, and an antiferromagnetic layer5 are formed in that order on a substrate 1 having large electricresistance. Respective layers from the lower ferromagnetic layer 2 tothe antiferromagnetic layer 5 have a plane rectangular shape. Inaddition, a pair of lead electrodes 6a, 6b are formed in thelongitudinal direction at a distance on the antiferromagnetic layer 5,thus completing a magnetoresistive head. As materials constituting theselayers, an iron-manganese (NiFe) is used as upper and lowerferromagnetic layers 2, 4, a copper (Cu) is used as the antimagneticmetal layer 3, and an iron-manganese (FeMn) is used as theantiferromagnetic layer 5, for example. In FIGS. 1A and 1B, a Z-axisdenotes the direction of film thickness.

The upper ferromagnetic layer 4 is magnetized by exchange coupling ofthe antiferromagnetic layer 5, and the direction of magnetization is awidth direction (an X axis direction in FIG. 1B). The lowerferromagnetic layer 2 is magnetized in the longitudinal direction (a Yaxis direction in FIG. 1B). It is preferable that the direction ofmagnetization of the lower ferromagnetic layer 2 intersects orthogonallythe direction of magnetization of the upper ferromagnetic layer 4 if theexternal signal magnetic field is zero. The external signal magneticfield is a magnetic field generated from the magnetic recording medium,and is generated in the width direction of each layer (an X axisdirection). The direction of magnetization of the upper ferromagneticlayer 4 is perpendicular to the surface of the magnetic recording mediumwhereas the direction of magnetization of the lower ferromagnetic layer2 is formed along the surface of the magnetic recording medium.

If the external signal magnetic field is applied to such spin valvemagnetoresistive head, the direction of magnetization of the lowerferromagnetic layer 2 is inclined at an angle corresponding to thestrength and direction of the external signal magnetic field.

A component of the direction of magnetization of the lower ferromagneticlayer 2 in the direction opposite to the direction of magnetization ofthe upper ferromagnetic layer 4 causes scattering of electrons passingthrough these layers, thus increasing electric resistance of entirelayers. On the other hand, a component of the direction of magnetizationof the lower ferromagnetic layer 2 in the same direction as thedirection of magnetization of the upper ferromagnetic layer 4 decreasesscattering of electrons passing through these layers, thus decreasingelectric resistance of entire layers.

The electric resistance of the sense current area S is changed inproportion to cosine of angle difference θ between the direction ofmagnetization of the lower ferromagnetic layer 2 and the direction ofmagnetization of the upper ferromagnetic layer 4, i.e., cosθ.

In addition, in order to change the electric resistance to the signalmagnetic field generated from the magnetic recording medium linearly,the direction of magnetization of the lower ferromagnetic layer 2 isintersected with the direction of magnetization of the upperferromagnetic layer 4 under the condition that the external signalmagnetic field is zero. This signal magnetic field is applied to thesame direction as or the opposite direction to the direction ofmagnetization of the upper ferromagnetic layer 4, i.e., the fixeddirection of magnetization.

Thereby, as shown in FIG. 1C, a relation between the external signalmagnetic field H and the electric resistance ΔR[R(H)-Ro(H=0)] can bederived.

In case the signal magnetic field generated by the magnetic recordingmedium is converted into an electric signal, a change in the electricresistance due to the signal magnetic field can be converted into achange in electric voltage by passing a constant current between a pairof lead electrodes 6a, 6b. The change of the voltage is used as areproducing electric signal. This is the same in the embodimentsdescribed hereinafter.

In addition, a width of a sense area S which reads a signal magneticfield by a spin valve magnetoresistance effect has been defined by adistance between the pair of lead electrodes 6a, 6b.

However, according to the laminated layer structure shown in FIG. 1A, aleakage magnetic field from a side portion of the upper ferromagneticlayer 4 enters into a side portion of the lower ferromagnetic layer 2and acts as a bias magnetic field even when the external signal magneticfield is in a zero state.

Therefore, the direction of magnetization of the lower ferromagneticlayer 2 made of a soft magnetic material is inclined by the leakagemagnetic field, so that the direction of magnetization of the lowerferromagnetic layer 2 does not intersect orthogonally with themagnetization of the upper ferromagnetic layer 4. As a result, there iscaused a drawback that the electric resistance (specific resistance)cannot change linearly with respect to the signal magnetic field andthus the voltage waveform as a reproducing signal is distorted.

On the contrary, a magnetoresistive head wherein the direction ofmagnetization of the upper magnetic layer is not fixed and varied by theexternal signal magnetic field along with the direction of magnetizationof the lower magnetic layer has been set forth in Patent ApplicationPublication (KOKAI) 2-61572. But, although influence of the leakagemagnetic field from the ferromagnetic layer need not be considered,there is no recitation in this Publication how to adjust a relativeangle between directions of magnetization of two ferromagnetic layersconcretely. In practice, it is hard to operate the magnetoresistive headlinearly by intersecting directions of magnetization of these layerswith each other.

As shown in FIG.2, a signal magnetic field H_(t) of a track adjacent tothe magnetic recording medium beneath the lead electrode 6a leaks intothe sense area S via soft magnetic layers 2, 4 formed immediately belowthe lead electrodes 6a, 6b. Therefore, there has been caused anotherdrawback that noise enters into a reproducing electric signal.

In addition, the sense area S must be defined essentially by thedistance between two lead electrodes 6a, 6b. However, the spin valvemagnetoresistance effect is in practice caused in a wider area than thatdefined by the distance between two lead electrodes 6a, 6b. Thus, therehas been caused another drawback that the sense area for reading thesignal magnetic field becomes vague, so that it is difficult to clearlydefine the sense area.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a magnetoresistive headcapable of eliminating distortion in an output characteristic of achange in electric resistance caused by the signal magnetic field.

Another object of the present invention is to provide a magnetoresistivehead capable of defining the width of the sense area for reading thesignal magnetic field with precision, and also suppressing the noisefrom entering into the reproducing electric signal.

According to an aspect of the present invention, a first magnetic layer,a second magnetic layer and a third magnetic layer are formed throughnonmagnetic metal layers in order to separate magnetically, and a senseelectric current is supplied to at least the second magnetic layer andthe third magnetic layer and the second nonmagnetic metal layerinterposed therebetween in the same direction as and the oppositedirection to the direction of magnetization of the second magneticlayer.

Therefore, the first magnetic layer and the third magnetic layer aremagnetized in the direction perpendicular to the direction ofmagnetization of the second magnetic layer by the magnetic fieldgenerated by the sense current therearound. Since normally this sensecurrent is constant current, the strength of magnetization is notchanged. Only the direction of magnetization of the second magnetizationlayer is rotated by the signal magnetic field from the magneticrecording medium.

In this case, the first and third magnetic layers are magnetized by thesense current and coupled magneto-statically to each other. Therefore,since the leakage magnetic fields leaked from the side portions of thefirst and third magnetic layers can be coupled mutually, they are neverapplied to the second magnetic layer.

In addition, since, under the condition where the sense current isflowing and there is no signal magnetic field from the magneticrecording medium, the direction of magnetization of the second magneticlayer is intersected orthogonally with at least the direction ofmagnetization of the third magnetic layer, the change rate of theelectric resistance can change linearly with respect to the change ofthe signal magnetic field, and thus there is caused no distortion of thevoltage waveform at the time of reproducing.

If the sense current can be flown in all layers from the first magneticlayer to the third magnetic layer by reducing the specific resistance ofthe first and second nonmagnetic metal layers, the spin valvemagnetoresistance effect is caused in the first, second and thirdmagnetic layers. Therefore, the change of the electric resistance can beincreased to thus improve the reproducing sensitivity.

In this case, if the product of the saturation magnetization of thefirst magnetic layer and its film thickness and the product of thesaturation magnetization of the third magnetic layer and its filmthickness are set to be equal to each other, these layers are balancedmagnetically and become stable.

According to the present invention, the first soft magnetic layer andthe second soft magnetic layer, both being magnetized in the oppositedirection to each other, are laminated via the nonmagnetic layer, andthe magnetization direction adjusting layer which generates the magneticfield intersecting orthogonally with the easy magnetization axis of thefirst and second soft magnetic layers is formed. Thereby, since themagnetization of the first and second soft magnetic layers can berotated to intersect orthogonally with each other, a linearcharacteristic of the change of the specific resistance withoutdistortion can be derived with respect to the signal magnetic field.

In addition, since the magnetization direction adjusting layer is formedon the first soft magnetic layer, miniaturization of themagnetoresistive head is never interrupted.

As the magnetization direction adjusting layer, there is the nonmagneticlayer formed on the first soft magnetic layer via the insulating layer.The magnetic field which rotates magnetization of the first and secondsoft magnetic layers to thus intersect them with each other is generatedby flowing the electric current in the nonmagnetic metal layer.According to this structure, the directions of magnetization of thefirst and second soft magnetic layers can be finely adjusted bycontrolling the magnitude of the current.

In another magnetization direction adjusting layer, the hard magneticlayer is formed on the first soft magnetic layer via the insulatinglayer or the nonmagnetic layer, and the hard magnetic layer ismagnetized in the direction perpendicular to magnetization of the firstand second soft magnetic layers. According to this structure,magnetization of the first and second soft magnetic layers is rotatedfrom the easy magnetization axis by the leakage magnetic field of thehard magnetic layer.

In still another magnetization direction adjusting layer, the third softmagnetic layer is formed on the first soft magnetic layer via theinsulating layer or the nonmagnetic layer, and the third soft magneticlayer is magnetized by the magnetic field generated by the constantcurrent supplied to the first and second soft magnetic layers in thedirection perpendicular to magnetization of the first and second softmagnetic layers. The magnetization of the first and second soft magneticlayers is rotated from the easy magnetization axis by the bias magneticfield generated by the third soft magnetic layer.

According to the present invention, the nonmagnetic metal layer formedbetween the first soft magnetic layer and the second soft magnetic layeris formed only in the sense area. Therefore, since the area wherein thespin valve magnetoresistance effect is caused can be determined by thenonmagnetic metal layer forming region, the sense area can be definedprecisely. As a result, noise generated by the magnetic filed enteringinto the peripheral area of the sense area can be reduced.

In addition, the film thickness on both sides of the sense area in thenonmagnetic metal layer formed between the first soft magnetic layer andthe second soft magnetic layer is made thick. Therefore, since the spinvalve magnetoresistance effect is scarcely caused on both sides of thesense area, the sense area can be defined with accuracy by the formingregion of the thin nonmagnetic metal layer. As a result, noise generatedby the magnetic filed entering into the peripheral area of the sensearea can be reduced.

In addition, if the nonmagnetic metal layer formed on both sides of thesense area is formed thickly such that the nonmagnetic metal layer canbe used as the lead electrode, the thinner spin valve magnetoresistivehead may be formed.

Moreover, the first soft magnetic layer, on which the antiferromagneticlayer is not formed, of the first and second soft magnetic layers formedon and under the non-magnetic metal layer is formed only in the sensearea. Therefore, since the spin valve magnetoresistance effect is notcaused on both sides of the sense area, the sense area can be definedwith accuracy by the forming region of the first nonmagnetic metallayer. As a result, noise generated by the magnetic field entering intothe peripheral area of the sense area can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view showing a conventional spin valvemagnetoresistive head;

FIG. 1B is a perspective view showing the conventional spin valvemagnetoresistive head in FIG. 1A;

FIG. 1C is a characteristic view showing a relation between an externalsignal magnetic field and resistance;

FIG. 2 is a sectional view showing part of a spin valve magnetoresistivehead according to a conventional example;

FIG. 3A is a side view showing a magnetoresistive head according to afirst embodiment of the present invention;

FIG. 3B is a perspective view showing part of a laminated structure ofthe magnetoresistive head in FIG. 3A;

FIG. 3C is a perspective view showing a relation between electriccurrent and a magnetic field in case a sense current is supplied to themagnetoresistive head in FIG. 3A;

FIG. 4A is a side view showing a magnetoresistive head according to asecond embodiment of the present invention;

FIG. 4B is a perspective view showing part of a laminated structure ofthe magnetoresistive head in FIG. 4A;

FIG. 4C is a perspective view showing a relation between electriccurrent and a magnetic field in case a sense current is supplied to themagnetoresistive head in FIG. 4A;

FIG. 5A is a side view showing a spin valve magnetoresistive headaccording to a third embodiment of the present invention;

FIG. 5B is a perspective view showing part of the spin valvemagnetoresistive head in FIG. 5A;

FIG. 5C is a perspective view showing a state wherein the direction ofmagnetization is changed;

FIG. 6A is a side view showing a spin valve magnetoresistive headaccording to a fourth embodiment of the present invention;

FIG. 6B is a perspective view showing part of the spin valvemagnetoresistive head in FIG. 6A;

FIG. 7A is a side view showing a spin valve magnetoresistive headaccording to a fifth embodiment of the present invention;

FIG. 7B is a perspective view showing part of the spin valvemagnetoresistive head in FIG. 7A;

FIG. 8A is a sectional view showing a spin valve magnetoresistive headaccording to a sixth embodiment of the present invention;

FIG. 8B is a sectional view showing the spin valve magnetoresistive headaccording to the sixth embodiment of the present invention;

FIG. 9A is a sectional view showing a spin valve magnetoresistive headaccording to a seventh embodiment of the present invention;

FIG. 9B is a sectional view showing the spin valve magnetoresistive headaccording to the seventh embodiment of the present invention;

FIG. 10A is a sectional view showing the spin valve magnetoresistivehead according to the seventh embodiment of the present invention;

FIG. 10B is a sectional view showing the spin valve magnetoresistivehead according to the seventh embodiment of the present invention;

FIG. 11 is a sectional view showing a spin valve magnetoresistive headaccording to an eighth embodiment of the present invention;

FIGS. 12A to 12D are sectional views each showing methods ofmanufacturing a spin valve magnetoresistive head according to a ninthembodiment of the present invention;

FIG. 13A is a sectional view showing a composite type MR head havingtherein the spin valve magnetoresistive head according to a tenthembodiment of the present invention;

FIG. 13B is a sectional view showing an in-gap type MR head havingtherein the spin valve magnetoresistive head according to the tenthembodiment of the present invention; and

FIG. 13C is a sectional view showing a yoke type MR head having thereinthe spin valve magnetoresistive head according to the tenth embodimentof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

There will now be described preferred embodiments of the presentinvention hereinafter with reference to the accompanying drawings.

First Embodiment

FIG. 3A is a sectional view showing a magneto-resistance transduceraccording to a first embodiment of the present invention. FIG. 3B is aperspective view showing the magnetoresistive head in FIG. 3A.

As shown in FIGS. 3A and 3B, a first magnetic layer 12 having a filmthickness of 5 to 10 nm, a first nonmagnetic metal layer 13 having afilm thickness of 5 to 10 nm, a second magnetic layer 14 having a filmthickness of 3 to 10 nm, a second nonmagnetic metal layer 15 having afilm thickness of 2 to 4 nm, and a third magnetic layer 16 having a filmthickness of 3 to 10 nm are formed in that order on a substrate 11having large electric resistance.

Respective layers from the first magnetic layer 12 to the third magneticlayer 16 are grown by sputtering, evaporation etc. in the same vacuumchamber. When being grown, the first magnetic layer 12, the secondmagnetic layer 14 and the third magnetic layer 16 are magnetized byexternal magnetic fields from the particular direction. In addition,respective layers from the first magnetic layer 12 to the third magneticlayer 16 are patterned by ion milling using a resist mask (not shown) tohave a rectangular plane shape. As shown in FIG. 3B, the rectangularplane shape has the direction of magnetization in the longitudinaldirection, and has a long side (y axis direction) of 10 to 100 μm and ashort side (x axis direction) of 1 to 5 μm. The direction of the shortside is also referred to as the width direction hereinbelow. The z axisdirection is set to the direction of the film thickness.

The first magnetic layer 12 is formed with a soft magnetic materialwhich is made of, for example, either one of an iron-nickel (NiFe) film;the NiFe film into which an element such as chromium (Cr), niobium (Nb),molybdenum (Mo) or vanadium (V) is added; a simple substance film ofcobalt (Co) or nickel (Ni) or an alloy film including cobalt (Co) ornickel (Ni); an iron (Fe) film; and a Co system amorphous film.

The first nonmagnetic metal layer 13 is formed with a material such astantalum (Ta) or titanium (Ti) which has larger electric resistivity(specific resistance) than that of the second magnetic layer 14. Thesecond magnetic layer 14 is formed with a soft magnetic material such asNiFe. The second nonmagnetic metal layer 15 is formed with a metal suchas copper (Cu) or gold (Au) which has small specific resistance. Thethird magnetic layer 16 is formed with a material such as NiFe or cobaltwhich has specific resistance equal to or larger than that of the secondmagnetic layer 14. The first nonmagnetic metal layer 13 and the secondnonmagnetic metal layer 15 are provided to isolate magnetically thefirst magnetic layer 12, the second magnetic layer 14 and the thirdmagnetic layer 16, respectively.

In addition, on the third magnetic layer 16, a first and second leadelectrodes (electric current supplying layers) 17a and 17b are formed bya lift-off method so as to put a sense area A therebetween in thelongitudinal direction. The first and second lead electrodes 17a and 17bare formed with an Au film having a thickness of 100 to 200 nm.

In the magnetoresistive head so constructed as aforementioned, when asignal magnetic field H_(sig) is read from a magnetic medium, sensecurrent I is supplied to the sense area A formed between the first andsecond lead electrodes 17a and 17b by connecting the electrodes 17a and17b to a constant current source (not shown). The sense current I isflown in the direction either identical to the direction ofmagnetization of the second magnetic layer 14 or opposite thereto.

Consequently, as shown in FIG. 3C, the first magnetic layer 12 and thethird magnetic layer 16 are mutually coupled magnetostatically by amagnetic field H₁ (shown by a broken line in FIG. 3C) which is generatedby the sense current I based on an Ampere's right-handed screw rule.

Therefore, as shown by a solid line arrow in FIG. 3C, leakage magneticfields leaked out from a side portion of the first magnetic layer 12 anda side portion of the third magnetic layer 16 are coupled, and thus theycannot enter into the second magnetic layer 14 formed between the firstmagnetic layer 12 and the third magnetic layer 16. In addition, since amagnetic field H₁ is generated by the sense current I therearound in thedirection perpendicular to the direction of magnetization of the secondmagnetic layer 14, at least the direction of magnetization of the thirdmagnetic layer 16 is changed by the magnetic field H₁, as shown in FIG.3C, so as to intersect orthogonally the direction of magnetization ofthe second magnetic layer 14. The direction of magnetization of thefirst magnetic layer 12 is directed in the opposite direction to thedirection of magnetization of the third magnetic layer 16. According tothe material of the first magnetic layer 12, the direction ofmagnetization of the first magnetic layer 12 is opposed to the directionof magnetization of the third magnetic layer 16 or is slightly inclinedagainst the direction of magnetization of the third magnetic layer 16.

Thereby, under the condition wherein there exists no signal magneticfield H_(sig) generated by a magnetic recording medium, the direction ofmagnetization of the third magnetic layer 16 is orthogonally intersectedwith the direction of magnetization of the second magnetic layer 14. Inresponse to a change in the signal magnetic field H_(sig), the directionof magnetization of the second magnetic layer 14 is rotated. However,since at least the third magnetic layer 16 is magnetized in the widthdirection, the direction of magnetization of the third magnetic layer 16is not rotated by the change in the signal magnetic field H_(sig).

Accordingly, no distortion in the change in the specific resistance ofthe second magnetic layer 14 and the third magnetic layer 16 is causedby the signal magnetic field H_(sig). As a result, there is nodistortion in output voltage which is converted into a reproducingsignal.

Since the first nonmagnetic metal layer 13 formed between the firstmagnetic layer 12 and the second magnetic layer 14 has large specificresistance, electric current hardly flows in the first magnetic layer12. As a result, the spin valve magnetoresistance effect cannot begenerated in the first magnetic layer 12.

Second Embodiment

A magnetoresistive head according to a second embodiment of the presentinvention is so constituted that the second nonmagnetic metal layerinterposed between the first magnetic layer and the second magneticlayer in the first embodiment is formed with a material having smallelectric resistance.

FIG. 4A is a sectional view showing a magnetoresistive head according tothe second embodiment. FIG. 4B is a perspective view showing themagnetoresistive head in FIG. 4A. The same parts as in FIGS. 3A and 3Bare denoted by the same reference symbols as used therein.

In FIGS. 4A and 4B, a first magnetic layer 12 having a film thickness of5 to 10 nm, a first nonmagnetic metal layer 13a having a film thicknessof 2 to 4 nm, a second magnetic layer 14 having a film thickness of 3 to10 nm, a second nonmagnetic metal layer 15 having a film thickness of 2to 4 nm, and a third magnetic layer 16 having a film thickness of 3 to10 nm are formed in that order on a substrate 11 having large electricresistance. The first nonmagnetic metal layer 13a and the secondnonmagnetic metal layer 15 are formed respectively with a materialhaving small electric resistance, for example, Au, Cu or the like. Inaddition, the first magnetic layer 12 and the third magnetic layer 16are designed such that their products of saturation magnetization andfilm thicknesses have the same values or the close values (within about10%) to each other.

Like the first embodiment, respective layers from the first magneticlayer 12 to the third magnetic layer 16 are formed to have a rectangularplane shape, a long side (y axis direction) of which is set in thedirection of magnetization.

In addition, on the third magnetic layer 16, first and second leadelectrodes 17a and 17b are formed by the same conditions as in the firstembodiment so as to put a sense area A therebetween.

In the magnetoresistive head so constructed as described above, underthe condition wherein the sense current I is supplied to the sense areaA, all the first magnetic layer 12, the second magnetic layer 14 and thethird magnetic layer 16 are magnetized in the longitudinal direction, asin the first embodiment. Further, when a signal magnetic field H_(sig)is read from a magnetic medium, the sense current I is supplied to thesense area A formed between the first and second lead electrodes 17a and17b by connecting the electrodes 17a and 17b to a constant currentsource. The sense current I is flown in the direction either identicalto the direction of magnetization of the second magnetic layer 14 oropposite thereto.

Since a magnetic field H₁ is generated by the sense current Itherearound in the direction perpendicular to the direction ofmagnetization of the second magnetic layer 14, the first magnetic layer12 and the third magnetic layer 16 are magnetized by the magnetic fieldH₁ in the direction intersected orthogonally with the direction ofmagnetization of the second magnetic layer 14.

Consequently, like the first embodiment, the first magnetic layer 12 andthe third magnetic layer 16 are mutually coupled magnetostatically bythe magnetic field H₁ which is generated by the sense current I. Thus, aleakage magnetic field leaked out from the first magnetic layer 12 and aleakage magnetic field leaked out from the third magnetic layer 16 arecoupled, and therefore they cannot enter into the second magnetic layer14 formed between the first magnetic layer 12 and the third magneticlayer 16.

Under the condition wherein there exists no signal magnetic fieldH_(sig) generated by a magnetic recording medium, magnetization of thefirst magnetic layer 12 and the third magnetic layer 16 is orthogonallyintersected with magnetization of the second magnetic layer 14. Thedirection of magnetization of the first magnetic layer 12 is opposite tothat of the third magnetic layer 16.

With the above, also in the second embodiment, the specific resistancecan be changed in response to the signal magnetic field withoutdistortion.

In the meanwhile, in the second embodiment unlike the first embodiment,not only the second nonmagnetic metal layer 15 but also the firstnonmagnetic metal layer 13a is formed with a material which has smallerspecific resistance than those of the second magnetic layer 14 and thethird magnetic layer 16. Therefore, the sense current I flowing betweenthe first and second lead electrodes 17a and 17b also flows into thefirst magnetic layer 12. Consequently, since, unlike the firstembodiment, the magnetoresistance effect can also be generated in thefirst magnetic layer 12, a rate of resistance change becomes large, sothat voltage converted when reproducing the signal magnetic field can beincreased. Thereby, read output can be increased to enhance sensitivityof the magnetoresistive head. Further, since respective products ofsaturation magnetization and the film thickness of the first magneticlayer 12 and the third magnetic layer 16 have the same values or thevery close values to each other, magnetostatical coupling between thembecomes stable.

As has been explained above, according to the second embodiment, thefirst, second and third magnetic layers are laminated through thenonmagnetic metal layers for isolating magnetically these magneticlayers, and the sense current is supplied to at least the second andthird magnetic layers and the nonmagnetic metal layer therebetween inthe direction either identical to the direction of magnetization of thesecond magnetic layer 14 or opposite thereto. Therefore, the first andthird magnetic layers are magnetized by the magnetic field generated bythe same current to be coupled magnetostatically to each other. Theleakage magnetic fields leaked out from side portions of the first andthird magnetic layers are prevented from being supplied to the secondmagnetic layer by mutually coupling them.

As a result, magnetization of the second magnetic layer cannot beinclined by the leakage magnetic fields, but can be rotated by thesignal magnetic field generated from the magnetic recording medium.Thus, the specific resistance can be changed linearly in response to thechange in the signal magnetic field, and it can be prevented thatdistortion in the voltage waveform is generated at the time ofreproducing.

If the sense current is supplied to all layers from the first magneticlayer to the third magnetic layer by forming the specific resistance ofthe first nonmagnetic metal layer to the second nonmagnetic metal layer,the spin valve magnetoresistance effect is caused in the first, secondand third magnetic layers. Thus, resistance change can be increased, andtherefore the reproducing sensitivity can be improved.

In this case, if respective products of saturation magnetization and thefilm thickness of the first magnetic layer and the third magnetic layerare set to have the same values or the very close values to each other,magnetostatical coupling between them can be stabilized.

Third Embodiment

FIG. 5A is a sectional view showing a magnetoresistive head according toa third embodiment of the present invention. FIG. 5B is a perspectiveview showing the magnetoresistive head in FIG. 5A. FIG. 5C is aperspective view showing a state wherein the direction of magnetizationis changed.

As shown in FIGS. 5A to 5C, a first nonmagnetic metal layer 22 having afilm thickness of 5 to 10 nm, an insulating layer 23 having a filmthickness of 5 to 50 nm, a first soft magnetic layer 24 having a filmthickness of 2 to 5 nm, a second nonmagnetic metal layer 25 having afilm thickness of 2 to 5 nm, and a second soft magnetic layer 26 havinga film thickness of 2 to 5 nm are formed on a substrate 21 having largeelectric resistance in that order by sputtering, evaporation etc. in thesame vacuum chamber. The first nonmagnetic metal layer 22 is used as amagnetization direction adjusting layer for the first soft magneticlayer 24 and the second soft magnetic layer 26.

The first soft magnetic layer 24 is magnetized in a first direction(Y-axis direction) in parallel to the face of the substrate 21 when itis grown. In addition, the second soft magnetic layer 26 is magnetizedin a second direction opposite to the first direction when it is grown.These magnetization M₁, M₂ are formed by applying the external magneticfield to the layers 24, 26. The first and second directions are easymagnetization axes (This is the same as in fourth and fifthembodiments.)

Respective layers formed on the substrate 21 are patterned by ionmilling using a resist mask (not shown) to have a rectangular planeshape. As shown in FIG. 5B, in the rectangular plane shape, directionsof magnetization M₁, M₂ of the first soft magnetic layer 24 and thesecond soft magnetic layer 26 are set to the longitudinal direction, anda long side (Y-axis direction) is 10 to 100 μm and a short side (X-axisdirection) is 1 to 5 μm, for example. The first nonmagnetic metal layer22 is formed to extrude from both ends of the longitudinal direction incontrast to other layers. The direction of the short side is alsoreferred to as the width direction hereinbelow. The z axis direction isset to the direction of the film thickness.

The first nonmagnetic metal layer 22 and the second nonmagnetic metallayer 25 are formed with a metal such as copper (Cu) or gold (Au) whichhas small specific resistance.

The first soft magnetic layer 24 and the second soft magnetic layer 26are formed with a soft magnetic material which is made of, for example,either one of an iron-nickel (NiFe) film; the NiFe film into which anelement such as chromium (Cr), niobium (Nb), molybdenum (Mo) or vanadium(V) is added; a simple substance film of cobalt (Co) or nickel (Ni) oran alloy film including cobalt (Co) or nickel (Ni); an iron (Fe) film;and a Co system amorphous film.

In order to isolate electrically the first non-magnetic metal layer 22from the layers formed thereabove, the isolating layer 23 is formedwith, for instance, alumina (Al₂ O₃) which is an inorganic isolatingmaterial.

In addition, first and second electrodes 29, 30 are formed by a lift-offmethod at both ends of the first nonmagnetic metal layer 22, while beingisolated from the first soft magnetic layer 24 and the second softmagnetic layer 26 and the second nonmagnetic metal layer 25. Third andfourth electrodes 27, 28 are formed by a lift-off method at both ends ofthe second soft magnetic metal layer 26, while being isolated from thefirst and second electrodes 29, 30. The first to fourth electrodes 27 to30 are formed with an Au film having a thickness of 100 to 200 nm. Asense area A is formed between the third and fourth electrodes 27, 28.

In the spin valve magnetoresistive head formed as above, as shown inFIG. 5C, when electric current I is supplied to the first nonmagneticmetal layer 22 formed between the first and second electrodes 29, 30 viathe electrodes 29, 30, a magnetic field H₁ is generated around the firstnonmagnetic metal layer 22. For this reason, the magnetization of thefirst soft magnetic layer 24 and the second soft magnetic layer 26 arerotated in reverse directions. As a result, an angle θ between bothdirections of magnetization is decreased. By adjusting a magnitude ofthe electric current I, the directions of magnetization are set to beintersected orthogonally (θ=90 degrees or 270 degrees) with each otherunder the condition when the external signal magnetic field H_(sig) iszero.

After adjusting the magnitude of the electric current I flowing in thefirst nonmagnetic metal layer 22, constant electric current I_(c) issupplied to the first soft magnetic layer 24, the second nonmagneticmetal layer 25 and the second soft magnetic layer 26 via the third andfourth electrodes 27, 28. In addition, when the signal magnetic fieldH_(sig) is applied in the width direction, magnetization M₁, M₂ of thefirst soft magnetic layer 24 and the second soft magnetic layer 26 arerotated according to the magnitude or the direction of the signalmagnetic field H_(sig). As a result, the angle θ between them is varied.Based on the angle θ, scattering state of conduction electrons in thefirst soft magnetic layer 24, the second nonmagnetic metal layer 25 andthe second soft magnetic layer 26 is varied to change the electricresistance. The change of the electric resistance is converted intovoltage and is then reproduced.

As described above, since, in the spin valve magnetoresistive head ofthe third embodiment, the directions of magnetization M₁, M₂ of thefirst soft magnetic layer 24 and the second soft magnetic layer 26 areadjusted by the magnetic field generated by the electric current flowingin the first nonmagnetic metal layer 22, the directions of magnetizationM₁, M₂ can be precisely intersected orthogonally with each other.Therefore, the electric resistance can be varied linearly. Besides,since both the magnetization of the first soft magnetic layer 24 and thesecond soft magnetic layer 26 can be rotated by the external signalmagnetic field H_(sig), a change rate of the electric resistance by aunit signal magnetic field can be increased in contrast to the casewhere only one of the layers 24 and 26 is rotated by the external signalmagnetic field H_(sig). As a result, sensitivity can be enhanced whenused as the magnetic information read device.

Further, only the first nonmagnetic metal layer 22 is formed on a rearface of the first soft magnetic layer 24 via the insulating layer 23.Therefore, the size of the device is never enlarged, and the request forthe miniaturization of the device can be satisfied.

It is preferable that both the direction of the current for adjustingthe direction of magnetization of the first soft magnetic layer 24 andthe second soft magnetic layer 26 and the direction of the constantcurrent I_(c) for attaining the spin valve magnetoresistance effect areset in the same direction. In other words, if the directions of thecurrent I, I_(c) are opposite to each other, magnetic fields caused bythe current I, I_(c) are negated mutually. Thus, the current I foradjusting the directions of magnetization M₁, M₂ of the first softmagnetic layer 24 and the second soft magnetic layer 26 has to beincreased to result in increased heat generation and external devicesare affected badly.

Fourth Embodiment

In a fourth embodiment, the directions of magnetization of a first softmagnetic layer and a second soft magnetic layer separated magneticallyare adjusted by a hard magnetic layer.

FIG. 6A is a sectional view showing a magnetoresistive head according tothe fourth embodiment. FIG. 6B is a perspective view showing themagnetoresistive head in FIG. 6A.

In FIGS. 6A and 6B, a hard magnetic layer 32 having a film thickness of5 to 10 nm, a magnetic separating layer 33 having a film thickness of 5to 50 nm, a first soft magnetic layer 34 having a film thickness of 2 to5 nm, a nonmagnetic metal layer 35 having a film thickness of 2 to 5 nm,and a second soft magnetic layer 36 having a film thickness of 2 to 5 nmare grown in that order on a substrate 31 having large electricresistance in the same vacuum chamber by sputtering, evaporation or thelike. The hard magnetic layer 32 is used as a magnetization directionadjusting layer for the first soft magnetic layer 34 and the second softmagnetic layer 36.

The first soft magnetic layer 34 is magnetized in a first direction(Y-axis direction) in parallel to the face of the substrate 31 when itis grown. In addition, the second soft magnetic layer 36 is magnetizedin a second direction opposite to the first direction when it is grown.The hard magnetic layer 32 is magnetized in the direction (X-axisdirection) intersected orthogonally with both the first direction andthe second direction.

The hard magnetic layer 32 is formed with, for example, CoCrPt,samarium-cobalt alloy, iron-neogium-boron alloy, barium ferrite. Themagnetic separating layer 33 is formed with a nonmagnetic layer such astantalum (Ta) and titanium (Ti) or an insulating layer such as Al₂ O₃.

The first and second soft magnetic layers 34, 36 and the nonmagneticmetal layer 35 are formed respectively with the material having the samefunction as shown in the first embodiment.

Respective layers formed on the substrate 31 are patterned by ionmilling using a resist mask (not shown) to have a rectangular planeshape. As shown in FIG. 6B, in the rectangular plane shape, directionsof magnetization of the first soft magnetic layer 34 and the second softmagnetic layer 36 are set to the longitudinal direction, and a long side(Y axis direction) is 10 to 100 μm and a short side (X-axis direction)is 1 to 5 μm, for example. The direction of the short side is alsoreferred to as the width direction hereinbelow. The Z-axis direction isset to the direction of the film thickness.

First and second electrodes 37, 38 made of Au having a film thickness of100 to 200 nm are formed by a lift-off method on both sides of the sensearea B of the second soft magnetic layer 36.

In the meanwhile, as shown in FIG. 6B, the direction of magnetization M₅of the hard magnetic layer 32 is intersected orthogonally with thedirections of magnetization M₃, M₄ of the first soft magnetic layer 34and the second soft magnetic layer 36 and is not coupled to the firstsoft magnetic layer 34 and the second soft magnetic layer 36 by exchangecoupling. However, the directions of magnetization M₃, M₄ of the firstsoft magnetic layer 34 and the second soft magnetic layer 36 are rotatedby the leakage magnetic field H₅ leaked from the hard magnetic layer 32.In this case, in order to change the resistance linearly by the signalmagnetic field, magnetization M₃, M₄ of the first soft magnetic layer 34and the second soft magnetic layer 36 must be intersected orthogonallywith each other in a state of no signal magnetic field H_(sig). Amagnitude of magnetization M₅ of the hard magnetic layer 32 is inadvance adjusted to provide a magnetic field which makes the directionsof magnetization M₃, M₄ intersect with each other.

This can be achieved if a sum of a product of an X-axis component of themagnetization M₃ of the first soft magnetic layer 34 and its filmthickness and a product of an X-axis component of the magnetization M₄of the second soft magnetic layer 36 and its film thickness is made tobe equal to a product of the magnetization M₅ of the hard magnetic layer32 and its film thickness.

In a state wherein constant electric current I_(c) is supplied to thefirst soft magnetic layer 34 and the second soft magnetic layer 36 inthe sense area B and the signal magnetic field H_(sig) is applied, if anangle between the directions of magnetization M₃, M₄ of the first softmagnetic layer 34 and the second soft magnetic layer 36 is smaller than90 degrees, scattering of conduction electrons is small and the electricresistance of the magnetoresistive head is decreased. On the contrary,if the angle is larger than 90 degrees, scattering of conductionelectrons is large and the electric resistance of the magnetoresistivehead is increased.

As described above, since the directions of magnetization M₃, M₄ of thefirst soft magnetic layer 34 and the second soft magnetic layer 36 areadjusted by the leakage magnetic field generated by the hard magneticlayer 32, the directions of magnetization M₃, M₄ can be preciselyintersected orthogonally with each other. Therefore, the electricresistance can be varied linearly. Besides, since both the magnetizationof the first soft magnetic layer 34 and the second soft magnetic layer36 can rotate by the signal magnetic field H_(sig), sensitivity can beenhanced like the third embodiment when used as the magnetic informationread device.

Further, only the hard magnetic layer 32 is formed on rear faces of thefirst and second soft magnetic layers 34, 36 via the magnetic separatinglayer 33. Therefore, the size of the device is never enlarged, and therequest for the miniaturization of the device can be satisfied.

In addition, since the fourth embodiment does not include theconfiguration for flowing the current, as in the third embodiment, inorder to incline the magnetization M₃, M₄ of the first soft magneticlayer 34 and the second soft magnetic layer 36, the configuration can besimplified.

Fifth Embodiment

In a fifth embodiment, the directions of magnetization of a first softmagnetic layer and a second soft magnetic layer separated magneticallyare adjusted by a soft magnetic layer.

FIG. 7A is a sectional view showing a magnetoresistive head according tothe fifth embodiment. FIG. 7B is a perspective view showing themagnetoresistive head in FIG. 7A.

In FIGS. 7A and 7B, a third hard magnetic layer 42 having a filmthickness of 5 to 10 nm, a magnetic separating layer 43 having a filmthickness of 5 to 50 nm, a first soft magnetic 44 having a filmthickness of 2 to 5 nm, a nonmagnetic metal layer 45 having a filmthickness of 2 to 5 nm, and a second soft magnetic layer 46 having afilm thickness of 2 to 5 nm are grown in that order on a substrate 41having large electric resistance in the same vacuum chamber bysputtering, evaporation or the like. The third hard magnetic layer 42 isused as a magnetization direction adjusting layer for the first softmagnetic layer 44 and the second soft magnetic layer 46.

The first soft magnetic layer 44 is magnetized in a first direction(Y-axis direction) in parallel to the face of the substrate 41 when itis grown. In addition, the second soft magnetic layer 46 is magnetizedin a second direction opposite to the first direction when it is grown.

Like the fourth embodiment, respective layers formed on the substrate 41are patterned by ion milling using a resist mask (not shown) to have arectangular plane shape.

The third soft magnetic layer 42 is formed with a soft magnetic materialwhich is made of, for example, either one of an iron-nickel (NiFe) film;the NiFe film into which an element such as chromium (Cr), niobium (Nb),molybdenum (Mo) or vanadium (V) is added; a simple substance film ofcobalt (Co) or nickel (Ni) or an alloy film including cobalt (Co) ornickel (Ni); an iron (Fe) film; and a Co system amorphous film.

The magnetic separating layer 43, the first soft magnetic 44, thenonmagnetic metal layer 45, and a second soft magnetic layer 46 arerespectively formed with materials having the same function as those inthe fourth embodiment.

First and second electrodes 47, 48 made of Au having a film thickness of100 to 200 nm are formed by a lift-off method on both sides of the sensearea C of the second soft magnetic layer 46.

In the meanwhile, as shown in FIG. 7B, constant electric current I_(c)is supplied to the first soft magnetic layer 44 and the second softmagnetic layer 46 in the sense area C and the nonmagnetic metal layer 45is via the first and second electrodes 47, 48. The magnetic field H₃ isgenerated by the constant electric current I_(c) and saturationmagnetization M₈ is formed in the hard magnetic layer 42 by the magneticfield H₃. The saturation magnetization M₈ of the hard magnetic layer 42is intersected orthogonally with the directions of magnetization M₆, M₇of the first soft magnetic layer 44 and the second soft magnetic layer46.

The directions of magnetization M₆, M₇ of the first soft magnetic layer44 and the second soft magnetic layer 46 are rotated by the leakagemagnetic field H₃ caused by the saturation magnetization M₈ in the hardmagnetic layer 42 to intersect both directions of magnetization M₆, M₇orthogonally with each other. This can be achieved if a sum of a productof an X-axis component of the magnetization M₆ of the first softmagnetic layer 44 and its film thickness and a product of an X-axiscomponent of the magnetization M₇ of the second soft magnetic layer 46and its film thickness is made to be equal to a product of themagnetization M₈ of the third soft magnetic layer 42 and its filmthickness.

Thereby, as in the fourth embodiment, a magnetic reading characteristicof the magnetoresistive head of the fifth embodiment is improved tooperate linearly.

In the fifth embodiment, since the magnetization direction adjustinglayers need not be magnetized like the fourth embodiment, there is anadvantage such that manufacturing labor can be saved upon fabricating.

As described above, according to the third to fifth embodiments, thefirst soft magnetic layer and the second soft magnetic layer, both beingmagnetized in opposite directions to each other, are laminated via thenonmagnetic layer, and the magnetization direction adjusting layerswhich generate magnetization intersecting orthogonally with the easymagnetization axis of the first soft magnetic layer and the second softmagnetic layer are formed so that the magnetic fields generated by thefirst soft magnetic layer and the second soft magnetic layer are rotatedto intersect orthogonally with each other. Thus, the specific resistancecan be changed linearly with respect to the signal magnetic field.

In addition, since only the magnetization direction adjusting layers canbe formed on the first soft magnetic layer, it can be prevented that thesize of the magnetoresistive head becomes large.

Sixth Embodiment

A spin valve magnetoresistive head according to a sixth embodiment willbe explained hereinafter. FIG. 8A is a sectional view showing the spinvalve magnetoresistive head according to the sixth embodiment.

In FIG. 8A, a reference 51 denotes a substrate made with alumina (Al₂O₃), a reference 52 denotes a first soft magnetic layer made with NiFe.The first soft magnetic layer 52 is formed by sputtering, evaporationetc. on the substrate 51 to have a film thickness of about 20 to 50 Å.

A reference 53 denotes a nonmagnetic metal layer made with Cu or Auformed on the first soft magnetic layer 52 by sputtering, evaporationetc. to have a film thickness of about 20 to 50 Å. Under the conditionwhere a sense area S is covered by a photoresist (not shown), thenon-magnetic metal layer 53 is patterned by ion milling method so as toleave a width of about 20 μm (Y-axis direction in FIG. 8A) between twolead electrodes 56a, 56b which are formed by later process.

Reference number 54 denotes a second soft magnetic layer made of NiFefilm which is formed on the first soft magnetic layer 52 and thenonmagnetic metal layer 53. The second soft magnetic layer 54 is formedby sputtering, evaporation etc. to have a film thickness of about 20 to50 Å.

Reference 55 denotes an antiferromagnetic layer made of FeMn film whichis formed on the second soft magnetic layer 54. The antiferromagneticlayer 55 is formed by sputtering, evaporation etc. to have a filmthickness of about 20 to 50 Å.

Magnetization of the second soft magnetic layer 54 is fixed in theX-axis direction in FIG. 8A by means of exchange coupling of theantiferromagnetic layer 55. And, in a no external magnetic field state,the first soft magnetic layer 52 is magnetized in the directionperpendicular to the direction of magnetization of the second softmagnetic layer 54 (Y-axis direction in FIG. 8A). The X-axis isintersected orthogonally with both the Z-axis (film thickness direction)and the Y-axis.

Respective layers from the first soft magnetic layer 52 to theantiferromagnetic layer 55 are patterned by ion milling to be left as arectangular plane shape.

First and second lead electrodes 56a, 56b made of Au having a filmthickness of about 100 to 200 nm are formed on the antiferromagneticlayer 55 in both areas of the nonmagnetic metal layer 53.

In case the signal magnetic field generated by the magnetic recordingmedium is converted into the electric signal by the spin valvemagnetoresistive head described advance, the change of the electricresistance caused correspondingly to the change of the signal magneticfield can be converted into the voltage change if the constant currentis flown between a pair of lead electrodes 56a, 56b. The voltage changecan be output as the reproducing electric signal.

According to the spin valve magnetoresistive head of the sixthembodiment, as shown in FIG. 8A, since the nonmagnetic metal layer 53 isformed only in the region between the lead electrodes 56a, 56b, thenonmagnetic metal layer 53 does not exist beneath the lead electrodes56a, 56b so that the first soft magnetic layer 52 directly contacts tothe second soft magnetic layer 54. Consequently, the magnetization ofthe first soft magnetic layer 52 right below the lead electrodes 56a,56b can be fixed by the antiferromagnetic layer 55 in the same direction(X-axis direction) as the magnetization of the second soft magneticlayer 54. Therefore, since the above spin valve magnetoresistance effectis not caused in this area, the sense area can be defined only by theregion between the lead electrodes 56a, 56b.

Therefore, according to the above spin valve magnetoresistive headaforementioned, even if the signal magnetic field generated by thenon-reading track adjacent to the reading track of the magneticrecording medium (not shown) enters into the area right below the leadelectrodes 56a, 56b, the spin valve magnetoresistance effect is nevercaused in such area. Therefore, the noise can be prevented from enteringinto the reproducing electric signal.

As a modification of the spin valve magnetoresistive head according to asixth embodiment, there will be a spin valve magnetoresistive head asshown in FIG. 8B. This modification has a reversely laminated structurein contrast to the structure shown in FIG. 8A.

In FIG. 8B, an antiferromagnetic layer 55 made of NiO film having a filmthickness of about 20 to 50 Å, and a second soft magnetic layer 54 madeof NiFe film having a film thickness of about 20 to 50 Å are formed inthat order on a substrate 51 made with alumina (Al₂ O₃). A nonmagneticmetal layer 53 made with Cu or Au formed on the second soft magneticlayer 54 in the sense area S. In addition, a first soft magnetic layer52 is formed on the nonmagnetic metal layer 53 and the second softmagnetic layer 54 to have a film thickness of about 20 to 50 Å. A firstand second lead electrodes 56a, 56b made of Au are formed on both sidesof the sense area S and on the first soft magnetic layer 52.

Also, in the spin valve magnetoresistive head shown in FIG. 8B, sincemagnetization of the first soft magnetic layer 52 located beneath thelead electrodes 56a, 56b is fixed by the antiferromagnetic layer 55 inthe X-axis direction identical to the second soft magnetic layer 54, thespin valve magnetoresistance is not caused. That is, the sense area Scan be defined by areas on which the nonmagnetic metal layer 53 isformed. As a result, noise caused by external magnetization generatedaround the sense area S can be reduced.

The width of the nonmagnetic metal layer 53 in the Y-axis direction andthe distance between the two lead electrodes 56a, 56b do not alwayscoincide with each other. The distance between the two lead electrodes56a, 56b may be set larger than the sense area S. However, the laminatedstructure formed of the first and second soft magnetic layers 52, 54 andthe antiferromagnetic layer 55 in the area having no nonmagnetic metallayer 53 increases the electric resistance, and there is a possibilitythat heat is generated when the current is passed into the laminatedstructure. Therefore, it is preferable that the width of the nonmagneticmetal layer 53 in the Y-axis direction and the distance between the twolead electrodes 56a, 56b are set to be equal to each other.

In addition, in the spin valve magnetoresistive head shown in FIG. 8B,although NiO has been used as the material of the antiferromagneticlayer 55, CoMn or NiMn may attain the same advantages.

Seventh Embodiment

A spin valve magnetoresistive head according to a seventh embodimentwill be explained hereinafter. FIGS. 9A and 9B and FIGS. 10A and 10B aresectional views showing the spin valve magnetoresistive head accordingto the sixth embodiment of the present invention.

In FIG. 9A, a first soft magnetic layer 62 made with NiFe is formed on asubstrate 61 made with alumina (Al₂ O₃). The first soft magnetic layer62 is formed by sputtering, evaporation etc. on the substrate 51 to havea film thickness of about 20 to 50 Å.

A nonmagnetic metal layer 63 made with Cu is formed on the first softmagnetic layer 62 by sputtering, evaporation etc. to have a filmthickness of about 20 to 50 Å. The nonmagnetic metal layer 63 is formedthickly on both sides of the sense area S to have a film thickness ofabout 20 to 50 nm and formed thinly in the sense area S to have a filmthickness of about 10 to 50 Å.

When forming the nonmagnetic metal layer 63, first a Cu film 63a isformed on entire surface of the first soft magnetic layer 62 bysputtering, evaporation etc. to have a film thickness of about 10 to 50Å, and then a Cu film 63b is formed on both sides of the sense area S bya lift-off method to have a film thickness of about 20 to 50 nm.

A second soft magnetic layer 64 made of NiFe film and anantiferromagnetic layer 65 made of FeMn film are formed in that order onthe nonmagnetic metal layer 63. A film thickness of these layers isabout 20 to 50 Å.

Magnetization of the second soft magnetic layer 64 is fixed in theX-axis direction in FIG. 8A by means of exchange coupling of theantiferromagnetic layer 65. And, in a no external magnetic field state,the first soft magnetic layer 62 is magnetized in the directionperpendicular to the direction of magnetization of the second softmagnetic layer 64 (Y-axis direction in FIG. 8A). The X-axis isintersected orthogonally with both the Z-axis (film thickness direction)and the Y-axis.

Respective layers from the first soft magnetic layer 62 to theantiferromagnetic layer 65 are patterned by ion milling to be left as arectangular plane shape.

A pair of lead electrodes 66a, 66b made of Au having a film thickness ofabout 100 to 200 nm are formed on the antiferromagnetic layer 65 and onboth sides of the sense area S.

The spin valve magnetoresistive head of the seventh embodiment alsoconverts the signal magnetic field generated by the magnetic recordingmedium into an electric signal in the same manner as in the sixthembodiment.

According to the seventh embodiment, as shown in FIG. 9A, thenonmagnetic metal layer 63 comprises a thin Cu film 63a having a filmthickness of about 10 to 50 Å formed in the sense area between a pair oflead electrodes 66a, 66b, and a thick Cu film 63b having a filmthickness of about 20 to 50 nm formed beneath a pair of lead electrodes66a, 66b.

Therefore, since a film thickness of the nonmagnetic metal layer 63b onboth sides of the sense area S is thick, the current passing between thelead electrodes 66a, 66b flows mainly in the thick nonmagnetic metallayer 63 in the area beneath the lead electrodes 66a, 66b. Thus, thespin valve magnetoresistance effect hardly occurs. In addition, since adistance between the first soft magnetic layer 62 and the second softmagnetic layer 64 is increased in the area beneath the lead electrodes66a, 66b, an interaction action of magnetization between the first softmagnetic layer 62 and the second soft magnetic layer 64 seldom occurs.As a result, the spin valve magnetoresistance effect can be extremelyreduced.

Thereby, the sense area S can be defined by the width of the nonmagneticmetal layer 63b between a pair of lead electrodes 66a, 66b withprecision.

As a modification of the spin valve magnetoresistive head according to aseventh embodiment, there will be a spin valve magnetoresistive head asshown in FIG. 9B. This modification has a reversely laminated structurein contrast to the structure shown in FIG. 8A.

In FIG. 9B, an antiferromagnetic layer 65 made of NiO film having a filmthickness of about 20 to 50 Å, and a second soft magnetic layer 64 madeof NiFe film having a film thickness of about 20 to 50 Å are formed inthat order on a substrate 61 made with alumina. A nonmagnetic metallayer 63 is formed on the second soft magnetic layer 64. The nonmagneticmetal layer 63 comprises a Cu film 63a having a film thickness of about10 to 50 Å formed in the sense area S, and a Cu film 63b having a filmthickness of about 20 to 50 nm formed beneath a pair of lead electrodes66a, 66b. In addition, a first soft magnetic layer 62 is formed on thenonmagnetic metal layer 63. A pair of lead electrodes 66a, 66b made ofAu are formed on both sides of the sense area S.

Also, in this modification, like the spin valve magnetoresistive headshown in FIG. 9B, since it is difficult to cause the spin valvemagnetoresistance effect in the area beneath the lead electrodes 66a,66b, the sense area S can be defined by the width of the thinnonmagnetic metal layer 63 formed between the lead electrodes 66a, 66bwith accuracy.

In the meanwhile, since the nonmagnetic metal layer 63 has a thick filmthickness on both sides of the sense area S, such thick film thicknessportions can be commonly used as the lead electrode. In other words, thestructure shown in FIGS. 10A and 10B may be employed by eliminating thelead electrodes 66a, 66b from the structure shown in FIGS. 9A and 9B. Inthis case, the lead electrodes are connected to the rectangular shapeareas of the first and second soft magnetic layers 62, 64 and thenonmagnetic metal layer 63.

Thereby, the spin valve magnetoresistive head can be obtained in a smallsize.

In addition, in the device shown in FIG. 9B, NiO has been used as theantiferromagnetic layer 65, but the present invention is not limited tosuch material. For example, CoMn or NiMn may attain the same advantage.In addition, as the material for the nonmagnetic metal layer 63, Au aswell as Cu may be used.

Eighth Embodiment

A spin valve magnetoresistive head according to an eighth embodimentwill be explained hereinafter. FIG. 11 is a sectional view showing thespin valve magnetoresistive head according to the eighth embodiment ofthe present invention.

In FIG. 11, a first soft magnetic layer 72 made with NiFe is formed in asense area S and on a substrate 71 made with alumina to have a filmthickness of about 20 to 50 Å. The first soft magnetic layer 72 isformed by sputtering, evaporation etc. on the substrate 71 and then ispatterned by ion milling and photolithography using a resist mask. Thefirst soft magnetic layer 72 has a width of 20 μm in the Y-axisdirection in FIG. 11.

A nonmagnetic metal layer 73 made with Cu, a second soft magnetic layer74 made of NiFe film and an antiferromagnetic layer 75 made of FeMnfilm, each having a film thickness of about 20 to 50 Å, are formed inthat order on the first soft magnetic layer 72 and the substrate 71 bysputtering, evaporation etc.

Magnetization of the second soft magnetic layer 74 is fixed in theX-axis direction in FIG. 11 by means of exchange coupling of theantiferromagnetic layer 75. And, in a no external magnetic field state,the first soft magnetic layer 72 is magnetized in the directionperpendicular to the direction of magnetization of the second softmagnetic layer 74 (Y-axis direction in FIG. 11). The X-axis isintersected orthogonally with both the Z-axis (film thickness direction)and the Y-axis.

Respective layers from the first soft magnetic layer 72 to theantiferromagnetic layer 75 are patterned by ion milling to be left as arectangular plane shape.

In addition, a pair of lead electrodes 76a, 76b made of Au are formed bya lift-off method on the antiferromagnetic layer 75 and on both sides ofthe sense area S.

The first soft magnetic layer 72 exists in the area between these leadelectrodes 76a, 76b.

In case the signal magnetic field generated from the magnetic recordingmedium is converted into the electric signal by the above spin valvemagnetoresistive head, the change of the electric resistance caused bythe change of the signal magnetic field is changed into the change ofthe voltage while the constant current flows between a pair of leadelectrodes 76a, 76b. The change of the voltage is output as thereproducing electric signal.

According to the eighth embodiment, as shown in FIG. 11, the first softmagnetic layer 72 is formed only in the area formed between these leadelectrodes 76a, 76b.

In this spin valve magnetoresistive head, the signal magnetic fieldgenerated from the magnetic recording medium is converted into theelectric signal in the same manner as in the sixth embodiment.

In this device, the spin valve magnetoresistance effect can be causedonly in the area wherein the first soft magnetic layer 72 is formed.Therefore, the spin valve magnetoresistance effect is never caused inthe area under the lead electrodes 76a, 76b. Thereby, the sense area Scan be defined with precision by the first soft magnetic layer 72between the lead electrodes 76a, 76b.

Consequently, the signal magnetic field on the non-read track adjacentto the read track becomes difficult to be input into themagnetoresistive head as noise.

In addition, in the spin valve magnetoresistive head shown in FIG. 11,Cu has been used as the nonmagnetic metal layer 73, but the presentinvention is not limited to such material. For example, any nonmagneticmetal layer such as Au may attain the same advantage. In addition,although FeMn has been used as the antiferromagnetic layer 75, thepresent invention is not limited to such material. For example, theantiferromagnetic material such as CoMn, NiMn or NiO may be used.

Ninth Embodiment

A spin valve magnetoresistive head according to a ninth embodiment willbe explained hereinafter with reference to FIGS. 12A to 12D along itsmanufacturing steps.

First, as shown in FIG. 12A, a antiferromagnetic layer 82 made with NiO,a second soft magnetic layer 83 made with NiFe, a nonmagnetic metallayer 84 made with Cu, and a first soft magnetic layer 85 formed withNiFe, each having a film thickness of 20 to 50 Å, are formed in thatorder on a substrate 81 made with alumina. Respective layers arepatterned to be left as a rectangular plane shape including a sense areaS, and then a resist film 86 is selectively formed on a surface of thefirst soft magnetic layer 85.

Then, as shown in FIG. 12B, the first soft magnetic layer 85 located inan area not covered by the resist film 86 is removed by ion millingusing the resist film 86 as a mask, so that the first soft magneticlayer 85a is left only in the sense area S.

Subsequently, as shown in FIG. 12C, an Au film 87a to 87c are depositedon an entire surface by sputtering to have a film thickness of about 100to 200 nm. Thereafter, as shown in FIG. 12D, a pair of lead electrodes87a, 87b are formed adjacent to both sides of the first soft magneticlayer 85a by removing the resist film 86 by a solvent, thus completingthe spin valve magnetoresistive head.

In the spin valve magnetoresistive head formed as above, as shown inFIG. 12D, the first soft magnetic layer 85a has been formed only in anarea formed between a pair of lead electrodes 87a, 87b.

In the spin valve magnetoresistive head, the spin valvemagnetoresistance effect can be caused only in the area wherein thelaminated structure composed of the first and second soft magnetic layer85a, 83 to put nonmagnetic metal layer 84 therebetween is formed. On theother hand, the spin valve magnetoresistance effect is not caused at allin the area just beneath the lead electrodes 87a, 87b wherein suchlaminated structure is not formed.

Thereby, like the eighth embodiment, since the sense area S can bedefined with precision between the lead electrodes 87a, 87b, the sensearea S is hardly affected by magnetic noise generated in the area exceptfor the sense area S.

Further, according to the steps shown in FIG. 12, since, uponfabricating the spin valve magnetoresistive head of the ninthembodiment, the resist film 86 which is used as a mask for selectivelyforming the first soft magnetic layer 85a by ion milling is commonlyemployed as the lift-off mask for selectively forming the leadelectrodes 87a, 87b, the fabricating steps can be simplified.

Furthermore, note that, although, in the device shown in FIG. 12D, Cuhas been used as the material of the non-magnetic metal layer 83, anonmagnetic conductive metal material such as Au may be used. Inaddition, note that, although NiO has been used as the material of theantiferromagnetic layer 82, CoMn, NiMn or FeMn, for example, may beused.

As has been described above, according to the sixth embodiment, sincethe nonmagnetic metal layer formed between the first soft magnetic layerand the second soft magnetic layer is formed only in the sense area, thesense area wherein the spin valve magnetoresistance effect is caused canbe defined precisely by the nonmagnetic metal layer forming region. As aresult, noise generated by the magnetic field entering into theperipheral area of the sense area can be reduced.

In addition, according to the seventh embodiment, since the filmthickness on both sides of the sense area in the nonmagnetic metal layerformed between the first soft magnetic layer and the second softmagnetic layer is made thick, the spin valve magnetoresistance effect isscarcely caused on both sides of the sense area, and the sense area canbe defined with accuracy by the forming region of the thin nonmagneticmetal layer. As a result, noise generated by the magnetic filed enteringinto the peripheral area of the sense area can be reduced.

In this device, if the nonmagnetic metal layer formed on both sides ofthe sense area is formed thickly such that the nonmagnetic metal layercan be used as the lead electrode, the thinner spin valvemagnetoresistive head may be formed.

Moreover, according to the third spin valve magnetoresistive head in theeighth and ninth embodiments of the present invention, since the firstsoft magnetic layer, on which the antiferromagnetic layer is not formed,of the first and second soft magnetic layers formed on and under thenonmagnetic metal layer is formed only in the sense area, the spin valvemagnetoresistance effect is not caused on both sides of the sense area.Therefore, the sense area can be defined with accuracy by the formingregion of the first nonmagnetic metal layer. As a result, noisegenerated by the magnetic filed entering into the peripheral area of thesense area can be reduced.

Tenth Embodiment

Next, with reference to FIGS. 13A to 13C, a magnetic recording apparatusaccording to the tenth embodiment of the present invention into whichthe MR device aforementioned is incorporated will be explained. FIGS.13A to 13C are sectional views each showing a magnetic head portion ofthe magnetic recording apparatus and a magnetic recording medium.

FIG. 13A shows a composite type MR head. An A portion denotes areproducing head, and a B portion denotes a recording head. A softmagnetic layer 102 is commonly used as a magnetic shield of thereproducing head and a magnetic pole of the recording head.

As shown in FIG. 13A, in the reproducing head portion, soft magneticlayers 101, 102 used as the magnetic shield are positioned at a distanceso as to oppose to each other. The MR device described above is put intoa gap of a portion 105 facing to a magnetic recording medium 106. Aleakage magnetic field generated from the magnetic recording medium 106can be directly detected.

In the reproducing head portion, soft magnetic layers 102, 104 used asthe magnetic pole are positioned at a distance so as to oppose to eachother. A coil 103 for generating magnetic flux flowing through the softmagnetic layers 102, 104 is formed in a gap between the soft magneticlayers 102, 104. By generating the leakage magnetic field from the gapof the facing portion 105 by this magnetic flux, the magnetic recordingmedium 106 can record various information.

According to this magnetic recording apparatus, since either one of theMR devices according to the first to ninth embodiments of the presentinvention is employed in the reproducing portion, distortion in anoutput characteristic of a change in electric resistance caused by thesignal magnetic field can be eliminated. In addition, the width of thesense area for reading the signal magnetic field can be definedprecisely, and the noise can be suppressed to enter into the reproducingelectric signal.

FIG. 13B shows an in-gap type MR head with flux guides. As shown in FIG.13B, soft magnetic layers 111, 114 used as the magnetic pole arepositioned at a distance so as to oppose to each other. The MR deviceaforementioned is put into a gap of a portion 115 facing to a magneticrecording medium 116. A coil 113 for generating magnetic flux passingthrough the soft magnetic layers 111, 114 is formed in a gap between thesoft magnetic layers 111, 114.

In order to avoid corrosion or direct contact to the magnetic recordingmedium, the MR device is positioned inside of the magnetic head not tobe protruded to the portion 115 facing to the magnetic recording medium116. A flux guide 112a which is electrically isolated from the MR deviceand magnetically coupled thereto is protruded to the facing portion 115.The leakage magnetic field generated by the magnetic recording medium116 is entered into the flux guide 112a and then detected by the MRdevice. At the other end of the MR device, another flux guide 112b whichis also electrically isolated from the MR device and magneticallycoupled thereto is formed to guide the magnetic flux passed through theMR device to the soft magnetic layers 111, 114.

According to this magnetic recording apparatus, since either one of theMR devices according to the first to ninth embodiments of the presentinvention is employed in the reproducing portion, distortion in anoutput characteristic of a change in electric resistance caused by thesignal magnetic field can be eliminated. Furthermore, the width of thesense area for reading the signal magnetic field can be defined withaccuracy, and the noise can be suppressed to enter into the reproducingelectric signal.

FIG. 13C shows a yoke type MR head. As shown in FIG. 13C, soft magneticlayers 121, 123a and 123b used as the magnetic pole are positioned at adistance so as to oppose to each other. A coil 122 for generatingmagnetic flux passing through the soft magnetic layers 121, 123a and123b is formed in a gap between the soft magnetic layers 121, 123a and123b. The MR device is positioned at ends of the soft magnetic layers123a and 123b such that it is electrically isolated from the softmagnetic layers 123a and 123b and magnetically coupled thereto. Theleakage magnetic field is generated from the gap of the facing portion124 by the magnetic flux, which is generated by the coil 122 and ispassed through the soft magnetic layers 121, 123a and 123b, to recordvarious information on the magnetic recording medium 125.

Also, in this case, according to this magnetic recording apparatus,since either one of the MR devices according to the first to ninthembodiments of the present invention is utilized in the reproducingportion, distortion in an output characteristic of a change in electricresistance caused by the signal magnetic field can be eliminated.Moreover, the width of the sense area for reading the signal magneticfield can be defined with precise, and the noise can be suppressed toenter into the reproducing electric signal.

In the magnetic recording apparatus shown in FIGS. 13A to 13C, asubstrate on which the magnetic head is formed and insulating filmsbetween the soft magnetic layers etc. are omitted.

Note that the MR device according to the present invention may be usedin various magnetic recording apparatus in addition to theaforementioned magnetic recording apparatus equipped with the recordingportion and the reproducing portion.

Moreover, the MR device may be used in a reproducing-only magneticrecording apparatus.

What is claimed is:
 1. A magnetoresistive sensor with spin valveconfiguration for detecting by a sense current a change of resistancedue to a signal magnetic field from a magnetic medium, saidmagnetoresistive sensor comprising:a first soft magnetic layer; a firstnonmagnetic metal layer formed on said first soft magnetic layer; asecond magnetic layer formed on said first nonmagnetic metal layer andhaving a magnetization direction in a direction of passing-through ofsaid sense current; a second nonmagnetic metal layer formed on saidsecond magnetic layer; a third soft magnetic layer formed on said secondnonmagnetic metal layer; and a sense current supplying layer forapplying said sense current to at least said second magnetic layer;wherein magnetization directions of said first and third soft magneticlayers are changed in response to said sense current while saidmagnetization direction of said second magnetic layer is changed inresponse to said signal magnetic field, any one of said first and thirdsoft magnetic layers being oriented in a given direction which isapproximately perpendicular to said direction of passing-through of saidsense current and another one of said first and third soft magneticlayers being oriented in a direction approximately opposite to saidgiven direction by a static magnetic coupling therebetween.
 2. Amagnetoresistive sensor according to claim 1, wherein said firstnonmagnetic metal layer has larger specific resistance than that of saidsecond nonmagnetic metal layer.
 3. A magnetoresistive sensor accordingto claim 1, wherein said first soft magnetic layer is a film selectedfrom a group consisting of an iron-nickel film, an iron film, and acobalt amorphous film.
 4. A magnetoresistive sensor according to claim1, wherein said first soft magnetic layer is an iron-nickel filmcontaining at least one selected from a group consisting of chromium,niobium, molybdenum, and vanadium.
 5. A magnetoresistive sensoraccording to claim 1, wherein said first soft magnetic layer is a singlefilm formed of one of cobalt and nickel.
 6. A magnetoresistive sensoraccording to claim 1, wherein said first soft magnetic layer is an alloyfilm containing at least one of cobalt and nickel.
 7. A magnetoresistivesensor according to claim 1, wherein said first nonmagnetic metal layerand said second nonmagnetic metal layer are a film having smallerspecific resistance than that of each of said first soft magnetic layer,said second magnetic layer and said third soft magnetic layer, and aproduct of saturation magnetization and a film thickness of said firstsoft magnetic layer has a value identical to or very close to a productof saturation magnetization and a film thickness of said third softmagnetic layer.
 8. A magnetoresistive sensor according to claim 7,wherein each of said first nonmagnetic metal layer and said secondnonmagnetic metal layer is a film formed of the same material, and hasthe same volume.
 9. A magnetic recording apparatus comprising amagnetoresistive sensor set forth in claim 1.